Chapter 1 Bpdu Tunneling Configuration; Introduction To Bpdu Tunneling; Why Bpdu Tunneling; How Bpdu Tunneling Works - H3C S9500 Series Operation Manual

Operation Manual – BPDU Tunneling
H3C S9500 Series Routing Switches

Chapter 1 BPDU Tunneling Configuration

1.1 Introduction to BPDU Tunneling

1.1.1 Why BPDU Tunneling

To avoid loops in your network, you can enable the spanning tree protocol (STP) on
your device. However, STP gets aware of the topological structure of a network by
means of bridge protocol data units (BPDUs) exchanged between different devices and
the BPDUs are Layer 2 multicast packets, which can be received and processed by all
STP-enabled devices on the network. This prevents each network from correctly
calculating its spanning tree. As a result, when redundant links exist in a network, data
loops will unavoidably occur.
By allowing each network has its own spanning tree while running STP, BPDU
tunneling can resolve this problem. It has the following functions:
It can isolate BPDUs of different customer networks, so that one network is not
affected by others while calculating the topological structure.
It enables BPDUs of the same customer network to be multicast over specific
VLAN VPNs in the service provider network, so that the same, geographically
dispersed customer network can implement consistent spanning tree calculation
across the service provider network.
Note:
At present, the S9500 series switches only support BPDU tunneling for STP packets (in
a broad sense). For description about STP packets in a broad sense, refer to the MSTP
Configuration in the Access Volume.

1.1.2 How BPDU Tunneling Works

The BPDU tunneling works implements the following two functions:
BPDU isolation
BPDU transparent transmission
The work process of IGMP is as follows:
I. BPDU isolation
When a port receives BPDUs of other networks, the port will discard the BPDUs, so that
they will not take part in spanning tree calculation. Refer to
Chapter 1 BPDU Tunneling Configuration
1-1
Configuring BPDU Isolation.